[edit]: You are right. The anthem was a navy song before, and is a part of the opera.

saw a production last night, that had the orchestra play the US national anthem and the entire audience sing it. there are portions of the anthem in the music of the opera

The Star Spangled Banner is a part of the opera, though not necessarily always in the introduction. The tune of the hymn is derived from an old British drinking song.

A few bars of the Star Spangled banner are part of the theme of Pinkerton but the whole anthem is not a part of then opera and the audience definitely do not sing it anywhere apart from in the US.

If it was performed in, say, North Korea or China, then the national anthem would be a likely introduction. But then again, it would be a different anthem likely.

Otherwise, I have to concur with previous posters.

I have seen the opera performed a number of times by different companies and have not ever seen that occur. It is true that a few bars are incorporated into the score as a theme associated with the American officer, Pinkerton, but the only singing is done onstage.